In one of his most important books, "Caddisflies", he discusses the different depths where trout primarily feed. What he writes makes us rethink some of the things we thought we knew. He says:
"Based on underwater observations the feeding percentages for each of the four zones are roughly:
Surface (top of the film) = 10%
Subsurface (bottom of the film) = 10%
Drift level = 60%
Bottom = 15%
Stray feeding at nonconcentration levels = 5%
The statement, "trout feed either at the top or bottom," by ignoring the two layers in between, fails to explain seventy percent of trout activity."
LaFontaine's book is filled with wisdom such as this. I would highly encourage all trout anglers to read it. (HERE, is a great place to buy it.)
If you're not familiar with LaFontaine or his work, I think you might enjoy learning more about this man who led a fascinating life. To learn more about him, click HERE. "Caddisflies" by Gary LaFontaine is a book that belongs in every angler's library.